Tetanus is caused by the action of the Clostridium tetani neurotoxin causing generalized muscle stiffness. This clever neurotoxin gains access to the CNS via retrograde transport up a peripheral nerve to the spinal cord, or brainstem (if it goes up a cranial nerve). Once in the spinal cord, it will irreversibly inhibit the inhibitory interneurons in the spinal cord thus resulting in generalized or partial muscle stiffness and spasm. Cats are more resistant to tetanus neurotoxin compared to humans or dogs, but they can still get the signs. Let’s talk about how to recognize this rare disease, in cats!
A recent retrospective study out of Europe (11 referral centers) was published in 2024 outlining signalment, clinical and neurologic findings, treatment and outcome. In this report, they cite that cats are thought to be 12 to 2400x more resistant to the toxin than humans or dogs. WOW!
This study described tetanus in 27 cats. Not surprisingly, this was mostly reported in the warmer months of spring, summer and fall with few cases in winter. It is interesting to note that this is not the case with dogs. More tetanus is reported in dogs in winter in Europe. The source of the infection was thought to be a wound in most cases; however, 5 cats had a recent history of sterilization.
The initial clinical signs were lameness or stiffness in a limb in 17/26 cats. This was noted as a difficulty manually flexing the joints in one or more limb on evaluation. Progression was noted in most of the cases, peaking at about 4 days from onset of signs. Two cats demonstrated tonic clonic seizures with loss of consciousness. Marked hyperthermia was noted in 10 cats. Unlike humans or dogs, generalized tetanus was less common in cats. Autonomic signs were rarely reported in cats but are more common in humans or dogs and may result in an increased mortality. Signs might include hypertension, hyperthermia, tachycardia, arrhythmias, profuse sweating and bradycardia. Three cases had wound cultures performed and all 3 were positive for Clostridium tetani.
Treatment
Hospitalization occurred in 21/27 cases with a mean hospitalization time of 7 days. Wound debridement was mentioned in 9/27 cats, along with antibiotics (26/27). Metronidazole was the most common antibiotic recommended, followed by Clavamox. The duration of antibiotic treatment was difficult to determine for many of the cats, but the authors report median treatment duration of 15 days (range 7-28). Muscle relaxation was facilitated with oral diazepam (21/27 cats) monotherapy or combined with methocarbamol, alfuzosin or magnesium sulfate (1 cat). Equine tetanus antitoxin was administered in 6/27 cats and no side effects were reported. The most common adverse effects reported included hyperthermia, urinary retention, dysphagia and osteoarticular disease (fractures due to muscle contractures or osteomyelitis). The more severe cases were noted to have adverse effects more commonly.
Outcome
Outcome was available for 25/27 cats. Of these, 23/25 (92%) regained independent motor within a median period of 25 days (range 11-42). The two cats that did not regain appropriate motor ultimately had limb amputation due to osteomyelitis.
What’s Take Away?
Even though more resistant, cats can get tetanus just like dogs. If you are presented with a cat with inappropriate focal stiffness and a wound, consider tetanus. Culturing the wound may aid in making a diagnosis. Metronidazole appears to successfully eliminate the infection, however due to the irreversible binding of the toxin the clinical signs may take longer to abate. When in doubt – refer for a consult!
Thanks for reading! I hope you have a wonderful week and enjoy this summer-like fall weather that we're having.
Reference: https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2024.1425917/full